I suppose that its not quite that simple.

I got into a bit of a bind while experimenting.

I was trying an alkaloid extraction and ended up with goo and brown liquid. My thoughts were that I would dissolve the alkaloid containing substance in distilled water, raise the PH (Sodium Hydroxide) and then the alkaloid would no longer be soluble in the water. Then I would use acetone to absorb the loose alkaloid and then have a near pure product via evaporation. The substance actually has two separate alkaloids in it, however their solubility constants in water are quite different, even across the PH scale, and thus with the PH balanced just right one would stay dissolved while the other would become suspended.

The problem I ran into (most chemists by now should know) is that acetone and water are miscible. This poses a problem to my experiment. So my question remains: Can you separate water and acetone while not interfering with what I am trying to do? I was thinking of adding a drying agent until the water will no longer stay mixed with the acetone, but I am afraid that this would interfere. I doubt that most drying agents would react with the alkaloids at all, however they may affect the PH of the solution and/or the total saturation of the alkaloids within either solution.

Distillation is not really an option because first, I don't have the setup for it yet, and second, it would just get me near pure acetone and an acetone/water/inert matter/alkaloid solution. Plus because of the azeotrope that would form, there would be a need of the drying solution anyway.

I know it seems necessary, but I don't wish to discuss the alkaloids I am trying to extract because of two reasons. I am not sure it would comply with the rules of the forum, and second I am trying (via experimentation) to develop a general method of alkaloid extraction; one that, with little modification, could be used on a wide range of alkaloids.

Anyway, I don't want to call this experiment a bust yet. It seems to me that the chemicals I have used thus far are easy to obtain at little cost, and also the alkaloid containing substance I started with would have to set me back a bit of money I don't want to have to pay again.

I am guessing that the "slime" hovering just above the bottom of the jar is the alkaloids forming a semi-cohesive ball because when I raised the PH they had nowhere to go, and even with the admission of acetone it uniformly mixed with the water also being unable to dissolve the alkaloids.

I can't use a filtration method, because the nature of the alkaloid in question. It seems to have a very fine particle size, even filter paper has trouble keeping it back.

Any help would be appreciated.
Thanks in advance.

When you're stuck in a hole, STOP DIGGING!! The best advice might well be to stop now and begin your extraction all over again. How long did that take when you first did it? Is the alkaloid source that expensive? Forget the hole, you have a lemon so let's make lemonade! (That's me - the man of a thousand cliches). If you don't have a distillation set-up, you don't have a ROTARY EVAPORATOR, do you? That's really what you need to just strip off the acetone.
We really need to know the amounts of water and acetone in your mixture. If there is a relatively small amount of acetone, you might be able to extract the acetone and alkaloids into ether (which is, of course, the solvent you should have used to begin.) To make this work better, you can saturate the water with sodium chloride. The high ionic strength greatly redjuces the solubility of organic solvents and you may find the acetone is no longer miscible. (Even without the ether) The danger is that you may have enough acetone to make a three component solution and you will be worse off than you were before! Test with water/acetone/ether solutions before you mess with the real thing.
You don't have to distill the acetone from the mixture. Maybe you should just heat the mixture in the hood with good stirring and evaporate or even boil off the acetone. By the way, I don't think acetone and water form an azeotrope, so don't worry about it. You can keep adding make-up water until you are convinced the acetone is gone. Then extract with ether like you should have used.
Good luck, Tell us how things are going, add details and we can offer additional suggestions.

I did try sodium salt,and that had little difference. I have used salt before to separate the water out of alcohol, but in this case it just seemed that the salt's solubility was greatly reduced. I had spent close to $50USD on the original substance, and I just don't want to spend any more. In reality the mixture is about 500mL acetone and another 500mL of water, sodium hydroxide, and the original substance mixed. The 500mL of the original mixture is actually about 30% of what I started with. I don't have equipment large enough to handle more than a liter at a time, so I won't be set back the whole $50 by throwing it. Aside from that, I would still like to see if it is recoverable.

I will try and see if ether will still grab the alkaloid with the acetone in it. I did a little research and found that acetone and water do not form an azeotrope, however when the ration is something like acetone to water 1:75 or something they do have azeotropic properties. I should just be able to heat the mixture (low temp safely) until it has about half of its original volume, then it will be 95% water and very little acetone. I will pick up some ether today and try it out.

Thanks for your response.

Just one thing first...

I know that some intermediate chemicals are added to make non-soluble substances become soluble. For instance, I know you can mix alcohol and water, and then the solution will actually be some what oil soluble. I am wondering if anyone has a clue as to whether the acetone will have any affect on the solubility of ether in water?

I will pour a small amount out of the bottle and test it to be sure, but insight is always nice too.

Ether is slightly soluble in water, in the presence of a significant amount of acetone I'm afraid it could have greatly increased solubility. Like I said, you could end up with a homogeneous solution of everything.
What equipment do you have available for your experiment You aren't doing this at home, on a stove are you? That would be extremely dangerous!!
Heat the water/acetone solution in a hood until the acetone seems gone -- you could gently boil it until the temperature reaches 100oC. Then you can do your ether extraction as before, The presence of a small amount of acetone shouldn't make much difference.
You may find it difficult to find a pH that allows a clean separation of the two alkaloids. Remember that an amine and its conjugate acid make a buffer system where there is little change in pH with added acid or base.

No, no this isn't exactly a kitchen experiment. I currently have the flask heated on an electric plate at about 65C. I figured the acetone would boil out and leave mostly water. It's not exactly in a hood, but it is well ventilated and I have a tube extending out the window. There is no vapor smell. I figure it will take a while as I am not heating at a very high temperature. There are however small bubbles of (what I am guessing to be) acetone forming on the side of the flask rising steadily. I will leave it heated probably for the remainder of the evening.

Post back in a couple of days -- I want reassurance that you are still alive! Place your flask in a pan of water, you will get better heat transfer and maybe the acetone will be eliminated more quickly. If you can bubble air or nitrogen through the contents of the flask that would help too. Please, be very carfeful.

Hi All,

I just read the Alkaloid discussion. Very impressive.

I am also working to isolate Alkaloid from my plant of interest.

Now at the end I am struck with Some greenish colour ppt, when I add Acetone-i get greenish brown solution which gives me two thick spot(Blue) with TLC and the remaining little white ppt (sticking at the bottom of beaker) when added CHCl3-CH3OH and spotted on TLC gave one Blue colour spot exactly same as as of acetone dissolved spot. Now I could confirm that there are two alkaloids altogether. Kindly help me out in Separating these two.

Thanks in advance

Arun KP